Liquid pump devices are typically installed at the mouths of containers, and are used for pumping liquid products inside the container out of the containers. In a typical liquid pump device, the liquid is pumped out of the container through up and down movement of the piston rod, such that the liquid is discharged from the discharge port. FIG. 1 illustrates a liquid pump device in the prior art. When a user presses the press head of the press pump, a lower one-way valve 180 is turned off, and an upper one-way valve 140 is turned on. The upper one-way valve is formed of the outer circumferential surface of a piston rod 152 and a piston member 141 installed on the circumferential surface. The outer circumferential surface of the piston rod 152 serves as a valve base, and the piston member 141 serves as a valve member. The liquid product in a liquid storage tank 130 in a cylinder 160 is conveyed out of the container through the turned-on upper one-way valve 140 and a conveying channel 151 of the piston 150, and a discharge channel 111 of the press head 110. The piston 150 is formed of the piston rod 152 and the piston member 141 on the piston rod 152, wherein the piston rod 152 and the piston member 141 simultaneously serve as members of the one-way valve 140 and the piston 150. To be specific, the one-way valve 140 is provided as a part of the piston 150. The conveying channel 151 and the discharge channel 111 form a distribution channel for pumping and distributing the liquid product from the liquid storage tank 130 to the outside of the container. When the user cancels the pressing onto the press head 110, the press head 110 restores to its original position under the action of an elastic restoration device 120; and during restoration of the press head 110, the lower one-way valve 180 is turned on, the upper one-way valve 140 is turned off, the liquid product in the container is suctioned by the lower one-way valve 180 to the liquid storage tank 130 for subsequent pumping and distribution. Generally, the distribution channel is arranged between the upper one-way valve 140 and an outlet portion 112 of the press head 110.
Such liquid pump device has a defect in terms of design. Specifically, upon completion of the press, pumping and distribution operations of the liquid pump device each time, liquid product still remains at the outlet portion of the press head, the liquid remain will trickle onto the surface where the container is placed or on the container, especially when the container is being moved or being replaced. As for liquid products (for example, oil-like or water-like products) with low viscosity and good flowability, even if the container is not moved and suffers from no shock, after a period of time, the liquid remain at the outlet portion approximate the press head will also trickle under the gravity, thereby causing undesired pollution.
Accordingly, it is desirable to provide a new-type liquid pump device